An incandescent lamp may fail when the filament breaks. If there is sufficient voltage applied, and there is sufficient atmosphere in the lamp, an uncontrolled arc may develope between the broken ends of the filament. The arc can cause the lamp to overheat, or break. To prevent an arcing failure, lamps may include a fuse to fail and cut off the arc. Presently press sealed lamps are fused by attaching a fuse nickel to the exterior end of the lead. The final contact point, such as a button contact, is then welded or crimped to the fuse. The fuse is small, and not easily attached in proper alignment. Welding the fuse to the button contact may further misalign the end connector. The result is a fused lamp with an offset, twisted or otherwise misaligned contact. The lamp then does not fit well in the lamp fixture, or makes a poor connection with the fixture contacts. When the lamp is coupled in the fixture, the poor contact alignment may cause the filament to be displaced from its expected optical position, thereby upsetting the lamp and fixture optics. There is then a need for a fused lamp with regular alignment.
The fuse is commonly a thin wire that is easily bent, and sometimes broken. It can therefore be difficult to make a proper weld to a thin fuse wire. The weld contact may not be made initially, or it make be broken in subsequent processing or use of the lamp. One know solution is to use an inner ceramic that locates and supports the fuse, but the extra ceramic piece requires separate manufacture, separate installation, and can be a separate source of manufacturing problems. The inner ceramic and its problems necessarily cost money to accommodate. There is then a need for a lamp design that protects the fuse from movement, and the possibility of misalignment, and breakage, and preferably one that is both simple and reliable. There is then a need for a lamp with internally pressed fuse.
Examples of the prior art are shown in the following U.S. patents.
U.S. Pat. No. 3,274,426 issued to R. F. Scoledge on Sep. 20, 1966 for Electric Lamp with Fuse shows a press sealed lamp with a fuse attached to the lead outside the press seal. The fuse is then enclosed by a ceramic end cap, and button contact structure.
U.S. Pat. No. 3,346,768 issued to G. F. Patsch on Oct. 10, 1967 for Incandescent Lamp with a Fuse Integral with the Lead in Structure shows a press sealed lamp with a fuse attached to the lead outside the press seal. The fuse is then enclosed by a ceramic end cap, and button contact structure. The fuse is entrained in the cement supporting the ceramic end cap.
U.S. Pat. No. 3,549,933 issued to John F. Smalley on Dec. 22, 1967 for Quartz Lamps shows a press sealed lamp with a looped outer lead extending from the seal foil. The loop is untrimmed, and no fuse is included in the lamp.
U.S. Pat. No. 3,710,169 issued to Germain R. T'Jampens on Jan. 9, 1973 for Halogen Filament Lamp Having an Internal All Protection Arrangement shows a press sealed lamp with a rod embedded on the inner side fo the seal foil to which the filament coil is attached. The embedded rod is said to provide a better fuse if the coil should break and the lamp move to an arc condition.